The present invention relates to lubricants for sewing threads and primarily to a flame retardant lubricant for use on a sewing thread employed in manufacturing nonflammable garments.
In the past, there have been a number of problems associated with the manufacture of nonflammable apparel, not the least of which related to the sewing thread employed in manufacturing such garments. Sewing threads require some type of lubrication in order to sew properly and to protect the thread from deteriorating due to the heat of friction created as the thread passes through the needle of the sewing machine. Most lubricants known in the trade today, however, are flammable and even the small amount of lubricant used, which may constitute from 2 to 10% of the total weight of the sewing thread, is so flammable that flammability of the seam occurs with the result that the original object, i.e., to have a nonflammable garment, is for all practical purposes destroyed.
This problem is further complicated by the fact that sewing threads currently in use for manufacturing nonflammable garments are generally of synthetic materials which exhibit thermoplastic properties. Such threads require even better lubrication than natural threads to ensure against needle burn.
It is therefore necessary and desirable in the manufacture of nonflammable apparel, to employ a sewing thread lubricated with a flame retarded lubricant. Such flame retardant lubricants known to the inventor in the past have been ordinary lubricants such as esters, mineral oils, paraffins, and other fatty acid derivatives which, although flammable in themselves, can be rendered nonflammable by the addition of fire-retardant materials such as compounds of halogens and phosphorus. These materials are only make-shifts, however, and the actual lubrication component is itself still flammable. Furthermore, the nonflammable portion of the combination generally has substantial nonlubricating properties which limit the lubrication value of the composite lubricant since the nonflammable portion often comprises as much as 8 or 10% of the total mixture.
In view of these difficulties with known lubricants, it was desirable to find a lubricant that had both lubricating and flame-retardant properties. It was discovered by this inventor that certain polybrominated esters of or compounds containing oleic or linoleic acid could be used for such a purpose.